Electronic devices, e.g. portable subscriber terminals of a mobile communication system, usually include a keyboard. As the devices are made smaller, the size of the keyboard can also be decreased. When pressing keyboard keys, the user may also press wrong keys. The small key size may increase the occurrences of wrong key presses. The dimensions of users' hands are different and the ways in which the keys are pressed also vary: some use the thumb whereas the others use the index finger. Thus the keyboard appearance is usually always a compromise; it suits an average user fine but has not been designed in accordance with the needs and routines of any individual user. As the use of different electronic devices provided with a keyboard is constantly becoming more common, there is a great need to enhance the ergonomics of keyboards.